Novel materials for use in various electronic devices, such as display devices and solar batteries, have been actively developed. In particular, research into novel materials that can replace indium tin oxide (ITO), which is generally used in forming a transparent electrode for electronic devices, has been actively performed. Among such novel materials, a carbon-containing material, such as carbon nanotubes, diamond, graphite, grapheme, or the like, is where the research is focused.
In particular, graphene has excellent electric conductivity and transparency, and due to such features, various methods for preparing graphene have been developed. Methods for preparing graphene can be largely classified into a mechanical method and a chemical method. An example of the mechanical method is separating graphene from a graphite sample by using a Scotch tape. This method does not damage the surface of graphene but is not suitable for a large-area graphene. An example of the chemical method is a chemical vapor deposition (CVD). According to CVD, a vaporous carbon supplier is placed in a container with catalytic metal located therein, and the container is heated and then cooled, thereby growing a graphene sheet on the surface of the catalytic metal.
Graphene prepared by CVD has grain boundaries which are formed by connecting several islands in an initial growth stage. Grain boundaries of graphene determine mobility properties associated with performance of a device. However, since grain boundaries of graphene can be identifiable under transmission electron microscope (TEM) or scanning tunneling microscope (STM), it is not easy to detect the grain boundaries of graphene.